Semiconductor light-emitting device and method for fabricating the device

ABSTRACT

An n-type AlAs/n-type Al 0.5 Ga 0.5 As DBR layer and a p-type (Al 0.2 Ga 0.8 ) 0.5 In 0.5 P/p-type Al 0.5 In 0.5 P DBR layer are formed on an n-type GaAs substrate at specified intervals so that a reflection spectrum is centered at 650 nm and the resonance wavelength becomes 650 nm. A quantum well active layer (light-emitting layer) is formed so that the light emission peak wavelength becomes 650 nm in the belly position of the standing wave generated in a resonator constructed of both the DBR layers. A grating pattern is formed on the surface of a p-type Al 0.5 Ga 0.5 As light diffusion layer that serves as a light-emitting surface surrounded by a p-type electrode. By thus roughening the light-emitting surface, light emitted from the light-emitting layer is diffused in various directions, reducing the radiation angle dependency of the emission light wavelength.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor light-emitting devicefor transmission use (in particular, for IEEE 1394), display use and thelike and a method for fabricating the device.

In recent years, semiconductor light-emitting devices are broadly usedfor optical communications and display panels. It is important for thesemiconductor light-emitting devices for the above uses to have a highlight emission efficiency, and it is further important for semiconductordevices for optical communications to have a high speed of response.Such devices have been actively developed lately.

The normal plane emission type LED's (light-emitting diodes) have aninsufficient high-speed response, which is limited to about 100 Mbps to200 Mbps. Accordingly, there is developed a semiconductor light-emittingdevice called the resonant-cavity type LED. This resonant-cavity typeLED is a semiconductor light-emitting device that achieves a high-speedresponse and high efficiency by controlling the natural emission lightwith a light-emitting layer placed in a belly position of a standingwave generated by a resonator formed of two mirrors (Japanese PatentPublication No. HEI 10-2744503, U.S. Pat. No. 5,226,053).

In particular, POF (plastic optical fiber) has lately started beingutilized for communications in a relatively short range, and there hasbeen developed a resonant-cavity type LED having a light-emitting layermade of an AlGaInP based semiconductor material capable of emitting withhigh efficiency light at a wavelength of 650 nm around which the POF hasa small loss (High Brightness Visible Resonant Cavity Light EmittingDiode: IEEE PHOTONICS TECHNOLOGY LETTERS Vol. 10, No. 12, DECEMBER1998).

However, the aforementioned conventional resonant-cavity type LED hasthe problems as follows. In detail, the conventional resonant-cavitytype LED has characteristics such that a resonant wavelength λ1 in theperpendicular direction and a resonant wavelength λ2 in a slantingdirection have a magnitude relation of λ1>λ2 and a peak wavelength isvaried depending on the angle of radiation from the LED chip. Normally,this radiation angle dependency is about 0.2 nm/deg to 0.3 nm/deg. Thiscauses a problem that the color is varied depending on the angle of viewwhen the LED chip is used for display.

When using the aforementioned LED chip for communications or as a lightsource for communications by means of, for example, a plastic fiber, anLED chip fabricated so as to have a peak at the wavelength of 650 nm atwhich the plastic fiber has a small loss in the perpendicular directioncannot be used in an optical system that utilizes the emission light ina slanting direction since the peak wavelength becomes shorter than 650nm.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to provide asemiconductor light-emitting device whose emission light wavelength hasa small radiation angle dependency and a method for fabricating thedevice.

In order to achieve the above object, there is provided a semiconductorlight-emitting device having a resonator constructed of a pair ofmulti-layer reflection films formed with interposition of a specifiedinterval on a GaAs substrate and a light-emitting layer formed in abelly position of a standing wave in the resonator, the devicecomprising:

a semiconductor layer which has one or more layers and an uppermostlayer whose surface is roughened, the semiconductor layer being formedon the multi-layer reflection film located on the opposite side of theGaAs substrate with respect to the light-emitting layer.

According to the above-mentioned construction, the surface of thesemiconductor light-emitting device is roughened. Therefore, as shown inFIG. 7A, light emitted from the light-emitting layer is diffused invarious directions when emitted out of the surface of the semiconductorlight-emitting device. As a result, the radiation angle dependency ofthe emission light wavelength is reduced.

In one embodiment of the present invention, the light-emitting layer isconstructed of an Al_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1) layer comprisedof a single layer or a plurality of layers.

According to the above-mentioned construction, the light-emitting layeris constructed of the Al_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1) layercomprised of a single layer or a plurality of layers. This enables theobtainment of emission light having a wavelength of 560 nm to 660 nm.

In one embodiment of the present invention, the multi-layer reflectionfilm located on the GaAs substrate side with respect to thelight-emitting layer is an Al_(x)Ga_(1−x)As (0≦x≦1) layer, and themulti-layer reflection film located on the opposite side of the GaAssubstrate with respect to the light-emitting layer is constructed of anAl_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1) layer.

According to the above-mentioned construction, the multi-layerreflection film located on the n-type GaAs substrate side with respectto the light-emitting layer is constructed of Al_(x)Ga_(1−x)As (0≦x≦1).Therefore, a difference in coefficient of thermal expansion from theGaAs substrate is small. Therefore, dislocation due to a differencebetween a temperature before crystal growth and a temperature aftercrystal growth is hard to occur. This allows the number of layers of themulti-layer reflection film to be increased and allows a highreflectance to be easily obtained.

The multi-layer reflection film located on the opposite side of the GaAssubstrate with respect to the light-emitting layer is formed ofAl_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1). Therefore, the layer that haslattice matching with the GaAs substrate includes Al at a maximum rateof about 25%, which is about one-half the rate of 50% in the case wherethe film is formed of Al_(x)Ga_(1−x)As (0≦x≦1). Therefore, moistureresistance is remarkably improved.

Also, there is provided a method for fabricating a semiconductorlight-emitting device having a resonator constructed of a pair ofmulti-layer reflection films formed with interposition of a specifiedinterval on a GaAs substrate 1 and a light-emitting layer formed in abelly position of a standing wave in the resonator, the methodcomprising:

a process for forming a semiconductor layer having one or more layers onthe multi-layer reflection film located on the opposite side of the GaAssubstrate with respect to the light-emitting layer; and

a process for roughening a surface of an uppermost layer of thesemiconductor layer.

According to the above-mentioned construction, the surface of theuppermost layer of the semiconductor layer formed on the resonatorconstructed of a pair of multi-layer reflection films is roughened.Therefore, light emitted from the light-emitting layer is diffused invarious directions when emitted out of the surface of the semiconductorlight-emitting device without reducing the reflectance of themulti-layer reflection films. As a result, the radiation angledependency of the emission light wavelength is reduced.

In one embodiment of the present invention, the roughening of thesurface of the uppermost layer of the semiconductor layer is performedby forming a light-difusing pattern by photolithography and etching.

According to the above-mentioned construction, the pattern that diffuseslight is formed on the surface of the uppermost layer of thesemiconductor layer by photolithography and etching. With thisarrangement, a high-accuracy fine pattern is formed. Therefore, thedegree of surface roughening is controlled so as to reduce the radiationangle dependency of the emission light wavelength.

In one embodiment of the present invention, the roughening of thesurface of the uppermost layer of the semiconductor layer is performedby abrasion.

According to the above-mentioned construction, the surface of theuppermost layer of the semiconductor layer is roughened by abrasion.This obviates the need for the complicated photolithographic process asin the case where the light diffusing pattern is formed, and asemiconductor light-emitting device is fabricated by a simpler method.

In one embodiment of the present invention, the semiconductor layer isformed of Al_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1), and

the roughening of the surface of the uppermost layer of thesemiconductor layer is performed by scalding at least the semiconductorlayer in hydrochloric acid.

According to the above-mentioned construction, the surface of theuppermost layer of the semiconductor layer is roughened by scalding thelayer in hydrochloric acid. This obviates the need for the processes ofsticking the entire wafer to another substrate, sheet or the like,holding the wafer and cleaning the wafer as in the case of theaforementioned abrasion. Therefore, a semiconductor light-emittingdevice is fabricated by a simpler method.

Also, there is provided a method for fabricating a semiconductorlight-emitting device having a resonator constructed of a pair ofmulti-layer reflection films formed with interposition of a specifiedinterval on a GaAs substrate 1 and a light-emitting layer formed in abelly position of a standing wave in the resonator, the methodcomprising:

a process for forming a semiconductor layer having one or more layersincluding an Al_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1) layer whose latticeconstant differs from the GaAs substrate by 0.5% or more on amulti-layer reflection film located on the opposite side of the GaAssubstrate with respect to the light-emitting layer, thereby roughening asurface of an uppermost layer of the semiconductor layer.

According to the above-mentioned construction, the surface of thesemiconductor layer formed on the multi-layer reflection film located onthe opposite side of the GaAs substrate with respect to thelight-emitting layer is roughened by the lattice constant difference.Through this process, the surface of the semiconductor layer isroughened only by a sequence of the crystal growth process. Thisobviates the need for providing a process for separately performing theroughening after the crystal growth, and a semiconductor light-emittingdevice is fabricated by a further simplified method.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a plan view of a semiconductor light-emitting device of thepresent invention;

FIG. 2 is a sectional view taken along the arrow line II—II in FIG. 1;

FIG. 3 is a view showing a fabricating process of the semiconductorlight-emitting device shown in FIG. 2;

FIG. 4 is a plan view showing a fabricating process subsequent to theprocess of FIG. 3;

FIG. 5 is a sectional view taken along the arrow line V—V in FIG. 4;

FIG. 6 is a graph showing a radiation angle dependency of the peakwavelength of the semiconductor light-emitting device shown in FIG. 1;

FIGS. 7A and 7B are explanatory views of an effect obtained by thesurface roughening of the semiconductor light-emitting device shown inFIG. 1;

FIG. 8 is a plan view of a semiconductor light-emitting device differentfrom that of FIG. 1;

FIG. 9 is a sectional view taken along the arrow line IX—IX in FIG. 8;

FIG. 10 is a view showing a fabricating process of the semiconductorlight-emitting device shown in FIG. 9;

FIG. 11 is a view showing a fabricating process subsequent to theprocess of FIG. 10;

FIG. 12 is a plan view showing a fabricating process subsequent to theprocess of FIG. 11;

FIG. 13 is a sectional view taken along the arrow line XIII—XIII in FIG.12;

FIG. 14 is a plan view of a semiconductor light-emitting devicedifferent from those of FIG. 1 and FIG. 8;

FIG. 15 is a sectional view taken along the arrow line XV—XV in FIG. 14;

FIG. 16 is a view showing a fabricating process of the semiconductorlight-emitting device shown in FIG. 15;

FIG. 17 is a plan view showing a fabricating process subsequent to theprocess of FIG. 16;

FIG. 18 is a sectional view taken along the arrow line XVIII—XVIII inFIG. 17;

FIG. 19 is a plan view showing a fabricating process subsequent to theprocess of FIG. 18;

FIG. 20 is a sectional view taken along the arrow line XX—XX in FIG. 19;

FIG. 21 is a plan view of a semiconductor light-emitting devicedifferent from those of FIG. 1, FIG. 8 and FIG. 14;

FIG. 22 is a sectional view taken along the arrow line XXII—XXII in FIG.21;

FIG. 23 is a view showing a fabricating process of the semiconductorlight-emitting device shown in FIG. 22;

FIG. 24 is a plan view showing a fabricating process subsequent to theprocess of FIG. 23;

FIG. 25 is a sectional view taken along the arrow line XXV—XXV in FIG.24;

FIG. 26 is a plan view showing a fabricating process subsequent to theprocess of FIG. 25;

FIG. 27 is a sectional view taken along the arrow line XXVII—XXVII inFIG. 26; and

FIG. 28 is a graph showing the radiation angle dependency of the peakwavelength of the semiconductor light-emitting device shown in FIG. 21.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail below on the basis ofthe embodiments thereof shown in the drawings.

<First Embodiment>

FIG. 1 is a plan view of a semiconductor light-emitting device of thepresent embodiment, while FIG. 2 is a sectional view taken along thearrow line II—II in FIG. 1.

The semiconductor light-emitting device of the present embodiment isbased on the AlGaInP system and is formed as follows. As shown in FIG.3, an n-type GaAs buffer layer 2 having a film thickness of 1 μm, ann-type AlAs/n-type Al_(0.5)Ga_(0.5)As 30-pair DBR (distributed Braggreflector) layer 3, an n-type (Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P firstclad layer 4, a quantum well active layer 5, a p-type(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second clad layer 6, a p-type(Al_(0.2)Ga_(0.8))_(0.5)P/p-type Al_(0.5)In_(0.5)P 12-pair DBR layer 7,a p-type Al_(0.5)Ga_(0.5)As current diffusion layer 8 having a filmthickness of 3 μm, a p-type (Al_(0.1)Ga_(0.9))_(0.5)In_(0.5)P etchingstop layer 9 having a film thickness of 0.1 μm and a p-typeAl_(0.5)Ga_(0.5)As light diffusion layer 10 having a film thickness of 3μm are successively laminated on an n-type GaAs substrate 1 having asurface whose normal line is inclined at an angle of 15° in the [011]direction from the (100) plane by the MOCVD (metal-organic chemicalvapor deposition) method. It is to be noted that the quantum well activelayer 5 has a well layer of GaInP and a barrier layer of(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P.

In this case, the n-type AlAs/n-type Al_(0.5)Ga_(0.5)As 30-pair DBRlayer 3 and the p-type (Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-typeAl_(0.5)In_(0.5)P 12-pair DBR layer 7 are formed so that the reflectionspectrum is centered at a wavelength of 650 nm, and a resonator lengthis adjusted so that the resonance wavelength of the resonator formed ofthe two DBR layers 3 and 7 becomes 650 nm. In the present embodiment,the resonator length was 1.5 times the wavelength. Further, the quantumwell active layer 5 is located in a belly position of a standing wavegenerated in the resonator, and the light emission peak wavelength isformed so as to become 650 nm.

Next, as shown in FIG. 4 and FIG. 5 (sectional view taken along thearrow line V—V in FIG. 4), an SiO₂ film 11 is formed on the surface ofthe p-type Al_(0.5)Ga_(0.5)As light diffusion layer 10 by the CVD(chemical vapor deposition) method, and a circular current path 14having a diameter of 70 μm is formed by photolithography and etchingwith diluted HF.

Subsequently, as shown in FIG. 1 and FIG. 2, AuZn/Mo/Au is sputtered onthe p-type Al_(0.5)Ga_(0.5)As light diffusion layer 10 and the SiO₂ film11 and patterned by photolithography to form a surface electrode. Then,a p-type electrode 12 is formed by performing heat treatment.

Subsequently, a 5-μm pitch grating pattern 15 is formed byphotolithography and sulfuric acid/hydrogen peroxide based etchantinside the circular current path 14 that belongs to the p-typeAl_(0.5)Ga_(0.5)As light diffusion layer 10 and is not provided with thep-type electrode 12. In this case, etching depth is controlled byperforming etching until the etching reaches the p-type(Al_(0.1)Ga_(0.9))_(0.5)In_(0.5)P etching stop layer 9. Then, the n-typeGaAs substrate 1 is abraded to a film thickness of about 280 μm, andAuGe/Au is deposited on this abraded surface and subjected to heattreatment to form an n-type electrode 13.

With regard to the thus-formed semiconductor light-emitting device, thegrating pattern 15 is formed in the p-type Al_(0.5)Ga_(0.5)As lightdiffusion layer 10 that serves as a light-emitting surface inside thecurrent path 14. Therefore, as shown in FIG. 7A, light emitted from thequantum well active layer 5 that serves as a light-emitting layer isdiffused in various directions when emitted to the outside.Consequently, as shown in FIG. 6, the radiation angle dependency of theemission light wavelength is made smaller than in the case where nograting pattern is formed in the p-type Al_(0.5)Ga_(0.5)Ga_(0.5)As lightdiffusion layer 10 (corresponding to the case of FIG. 7B).

The multi-layer reflection film (n-type AlAs/n-type Al_(0.5)Ga_(0.5)AsDBR layer) 3 located on the n-type GaAs substrate 1 side with respect tothe light-emitting layer (quantum well active layer) 5 is formed of anAlGaAs based material. Therefore, the occurrence of warp or a dark lineof the n-type GaAs substrate 1 is not observed since a difference incoefficient of thermal expansion with respect to the n-type GaAssubstrate 1 is small although the total film thickness is about 3 μm.Furthermore, by setting the number of layers to 30 pairs, a highreflectance of not lower than 99% is achieved.

The multi-layer reflection film (p-type(Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-type Al_(0.5)In_(0.5)P DBR layer) 7located on the opposite side of the n-type GaAs substrate 1 with respectto the light-emitting layer (quantum well active layer) 5 is formed ofan AlGaInP based material. Therefore, the layer that includes thegreatest quantity of Al in the vicinity of the surface isAl_(0.5)In_(0.5)P, and the moisture resistance does not matter.Furthermore, the peak reflectance of this multi-layer reflection film 7is about 70%, meaning that a sufficient reflectance is obtained as aresonant-cavity structure.

In the case of an Al_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1) multi-layerreflection film, dislocation tends to easily occur due to a differencein coefficient of thermal expansion between the layer and the n-typeGaAs substrate 1 if the number of layers exceeds 20 to 30 pairs.However, in the case of the resonant-cavity type LED, the multi-layerreflection film 7 located on the opposite side of the n-type GaAssubstrate 1 is not required to have a high reflectance that is requiredby the multi-layer reflection film 3 located on the n-type GaAssubstrate 1 side. Therefore, the multi-layer reflection film 7 is notrequired to have layers the number of which exceeds 20 pairs, and nodislocation occurs.

The semiconductor light-emitting device of the present embodiment wassubjected to an electrification test at a current of 50 mA under theconditions of a temperature of 80° and a humidity of 85%. An opticaloutput of 90% of the initial optical output was yielded even after alapse of 1000 hours. The present semiconductor light-emitting device hasa current constriction layer, and therefore, internal quantum efficiencyand external light emission efficiency are both high. With regard to theinitial optical output, a high optical output of 1.6 mW was able to beobtained at a current of 20 mA.

As described above, in the present embodiment, the n-type AlAs/n-typeAl_(0.5)Ga_(0.5)As DBR layer 3, and the p-type(Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-type Al_(0.5)In_(0.5)P DBR layer 7are formed with interposition of a specified interval on the n-type GaAssubstrate 1 so that the reflection spectrum is centered at thewavelength of 650 nm and the resonance wavelength becomes 650 nm. Then,the quantum well active layer (light-emitting layer) 5 is located in thebelly position of the standing wave generated in the resonatorconstructed of both the DBR layers 3 and 7 so that the emission lightpeak wavelength becomes 650 nm. Further, the grating pattern 15 isformed on the surface of the p-type Al_(0.5)Ga_(0.5)As light diffusionlayer 10 that serves as the light-emitting surface surrounded by thep-type electrode 12.

Therefore, the surface of the semiconductor light-emitting device of thepresent embodiment becomes a roughened surface, and the light emittedfrom the light-emitting layer 5 is diffused in various directions. As aresult, the radiation angle dependency of the emission light wavelengthcan be reduced.

The quantum well active layer 5 that serves as the light-emitting layeris formed of an Al_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1) layer constructedof a single layer or a plurality of layers. Therefore, light having awavelength of about 560 nm to 660 nm can be emitted.

<Second Embodiment>

FIG. 8 is a plan view of a semiconductor light-emitting device of thepresent embodiment, while FIG. 9 is

a sectional view taken along the arrow line IX—IX in FIG. 8.

The semiconductor light-emitting device of the present embodiment isbased on the AlGaInP system and is formed as follows. As shown in FIG.10, an n-type GaAs buffer layer 22 having a film thickness of 1 μm, ann-type AlAs/n-type Al_(0.5)Ga_(0.5)As 30-pair DBR layer 23, an n-type(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first clad layer 24, a quantum wellactive layer 25, a p-type (Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladlayer 26, a p-type (Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-typeAl_(0.5)In_(0.5)P 12-pair DBR layer 27 and a p-type Al_(0.5)Ga_(0.5)Ascurrent diffusion layer 28 having a film thickness of 10 μm aresuccessively laminated on an n-type GaAs substrate 21 having a surfacewhose normal line is inclined at an angle of 15° in the [011] directionfrom the (100) plane by the MOCVD method. It is to be noted that thequantum well active layer 25 has a well layer of GaInP and a barrierlayer of (Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P.

In this case, the n-type AlAs/n-type Al_(0.5)Ga_(0.5)As 30-pair DBRlayer 23 and the p-type (Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-typeAl_(0.5)In_(0.5)P 12-pair DBR layer 27 are formed so that the reflectionspectrum is centered at a wavelength of 650 nm, and a resonator lengthis adjusted so that the resonance wavelength of the resonator formed ofthe two DBR layers 23 and 27 becomes 650 nm. In the present embodiment,the resonator length was 1.5 times the wavelength. Further, the quantumwell active layer 25 is formed so that the layer is located in the bellyposition of the standing wave generated in the resonator with the lightemission peak wavelength set to 650 nm.

Subsequently, as shown in FIG. 11, the surface of the p-typeAl_(0.5)Ga_(0.5)As current diffusion layer 28 having a film thickness of10 μm is abraded by several micrometers to be roughened so that theemission light diffuses.

Next, as shown in FIG. 12 and FIG. 13 (sectional view taken along thearrow line XIII—XIII in FIG. 12), an SiO₂ film 29 is formed on thesurface of the p-type Al_(0.5)Ga_(0.5)As current diffusion layer 28 bythe CVD method, and a circular current path 32 having a diameter of 70μm is formed by photolithography and etching with diluted HF.

Subsequently, as shown in FIG. 8 and FIG. 9, AuZn/Mo/Au is sputtered onthe p-type Al_(0.5)Ga_(0.5)As current diffusion layer 28 and the SiO₂film 29 and patterned by photolithography to form a surface electrode.Then, a p-type electrode 30 is formed by performing heat treatment.Further, the n-type GaAs substrate 21 is abraded to a film thickness ofabout 280 μm, and AuGe/Au is deposited on this abraded surface andsubjected to heat treatment to form an n-type electrode 31.

The thus-formed semiconductor light-emitting device formed needs nocomplicated photolithography process when forming a grating pattern onthe wafer surface for the roughening of the surface and allows theprocesses to be simplified, by comparison with the first embodiment. Itis to be noted that the radiation angle dependency of the emission lightwavelength is sufficiently reduced similarly to the first embodiment.

With regard to the moisture resistance, there was no problem similarlyto the first embodiment. When an electrification test was performed at acurrent of 50 mA under the conditions of a temperature of 80° and ahumidity of 85%, an optical output of 90% of the initial optical outputwas yielded even after a lapse of 1000 hours. With regard to the initialoptical output, a high optical output of 1.6 mW was able to be obtainedat a current of 20 mA.

<Third Embodiment>

FIG. 14 is a plan view of a semiconductor light-emitting device of thepresent embodiment, while FIG. 15 is a sectional view taken along thearrow line XV—XV in FIG. 14.

The semiconductor light-emitting device of the present embodiment isbased on the AlGaInP system and is formed as follows. As shown in FIG.16, an n-type GaAs buffer layer 42 having a film thickness of 1 μm, ann-type AlAs/n-type Al_(0.7)Ga_(0.3)As 70-pair DBR layer 43, an n-type(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first clad layer 44, a quantum wellactive layer 45, a p-type (Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladlayer 46, a p-type (Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P/p-typeAl_(0.5)In_(0.5)P 18-pair DBR layer 47, a p-type AlGaInP intermediatelayer 48 having a film thickness of 0.15 μm, a p-type AlGaInP firstcurrent diffusion layer 49 having a film thickness of 1 μm, an n-typeAlGaInP current constriction layer 50 having a film thickness of 0.3 μmand an n-type GaAs cap layer 51 having a film thickness of 0.01 μm aresuccessively laminated on an n-type GaAs substrate 41 having a surfacewhose normal line is inclined at an angle of 15° in the [011] directionfrom the (100) plane by the MOCVD method. It is to be noted that thequantum well active layer 45 has a well layer of(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P and a barrier layer of(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P.

In this case, the n-type AlAs/n-type Al_(0.7)Ga_(0.3)As 70-pair DBRlayer 43 and the p-type (Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P/p-typeAl_(0.5)In_(0.5)P 18-pair DBR layer 47 are formed so that the reflectionspectrum is centered at a wavelength of 570 nm, and a resonator lengthis adjusted so that the resonance wavelength of the resonator formed ofthe two DBR layers 43 and 47 becomes 570 nm. In the present embodiment,the resonator length was 1.5 times the wavelength. Further, the quantumwell active layer 45 is formed so that the layer is located in the bellyposition of the standing wave generated in the resonator with the lightemission peak wavelength set to 570 nm.

Subsequently, as shown in FIG. 17 and FIG. 18 (sectional view takenalong the arrow line XVIII—XVIII in FIG. 17), the n-type GaAs cap layer51 is removed by a sulfuric acid/hydrogen peroxide based etchant.Thereafter, the n-type AlGaInP current constriction layer 50 is etcheduntil the etching reaches the p-type AlGaInP first current diffusionlayer 49 by photolithography and a sulfuric acid/hydrogen peroxide basedetchant. By this etching, a circular current path 55 having a diameterof 70 μm is formed.

Next, as shown in FIG. 19 and FIG. 20 (sectional view taken along thearrow line XX—XX in FIG. 19), a p-type AlGaInP second current diffusionlayer 52 having a film thickness of 7 μm is regrown on the n-typeAlGaInP current constriction layer 50 and the p-type AlGaInP firstcurrent diffusion layer 49.

Subsequently, as shown in FIG. 14 and FIG. 15, AuBe/Au is deposited onthe p-type AlGaInP second current diffusion layer 52, and a surfaceelectrode is formed by photolithography and etching with an Au etchant.Then, heat treatment is performed to form a p-type electrode 53. Next,the wafer is scalded in hydrochloric acid at a temperature of 65° C. to70° C. In this stage, the region that belongs to the surface of thep-type AlGaInP second current diffusion layer 52 and is not providedwith the p-type electrode 53 becomes a roughened surface. Further, then-type GaAs substrate 41 is abraded to a film thickness of about 280 μm,and AuGe/Au is deposited on this abraded surface and subjected to heattreatment to form an n-type electrode 54.

The thus-formed semiconductor light-emitting device does not need theprocesses of sticking the wafer to a sheet, another substrate or thelike, abrading the wafer, thereafter taking out the wafer and cleaningthe wafer at all for the purpose of abrading and roughening the wafersurface, by comparison with the second embodiment, allowing theprocesses to be simplified. It is to be noted that the radiation angledependency of the emission light wavelength is sufficiently reducedsimilarly to the first and second embodiments.

The multi-layer reflection film (n-type AlAs/n-type Al_(0.7)Ga_(0.3)As70-pair DBR layer) 43 located on the n-type GaAs substrate 41 side withrespect to the light-emitting layer (quantum well active layer) 45 isformed of an AlGaAs based material. Therefore, the occurrence of warp ora dark line of the n-type GaAs substrate 41 is not observed since adifference in coefficient of thermal expansion with respect to then-type GaAs substrate 41 is small although the total film thickness isabout 7 μm, which is thicker than those of the first and secondembodiments. As a result, the number of layers can be increased to 70pairs, allowing a high reflectance of not lower than 99% to be achieved.

The multi-layer reflection film (p-type(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P/p-type Al_(0.5)In_(0.5)P 18-pair DBRlayer) 47 located on the opposite side of the GaAs substrate 41 withrespect to the light-emitting layer (quantum well active layer) 45 isformed of an AlGaInP based material. Accordingly, there is no problemabout the moisture resistance, similarly to the first and secondembodiments. When an electrification test was performed at a current of50 mA under the conditions of a temperature of 80° and a humidity of85%, an optical output of 105% of the initial optical output was yieldedeven after a lapse of 1000 hours.

An initial optical output of 0.4 mW was provided as a consequence of anabout 10% increase in light take-out efficiency due to the dimensionalreduction in the area of branch-shaped electrodes 56 located above thelight-emitting portion, as compared with the first and secondembodiments.

<Fourth Embodiment>

FIG. 21 is a plan view of a semiconductor light-emitting device of thepresent embodiment, while FIG. 22 is a sectional view taken along thearrow line XXII—XXII in FIG. 21.

The semiconductor light-emitting device of the present embodiment isbased on the AlGaInP system and is formed as follows. As shown in FIG.23, an n-type GaAs buffer layer 62 having a film thickness of 1 μm, ann-type AlAs/n-type Al_(0.5)Ga_(0.5)As 30-pair DBR layer 63, an n-type(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first clad layer 64, a quantum wellactive layer 65, a p-type (Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladlayer 66, a p-type (Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-typeAl_(0.5)In_(0.5)P 12-pair DBR layer 67, a p-type AlGaInP intermediatelayer 68 having a film thickness of 0.15 μm, a p-typeAl_(0.01)Ga_(0.98)In_(0.01)P first current diffusion layer 69 having afilm thickness of 1 μm, an n-type Al_(0.01)Ga_(0.98)In_(0.01)P currentconstriction layer 70 having a film thickness of 0.3 μm and an n-typeGaAs cap layer 71 having a film thickness of 0.01 μm are successivelylaminated on an n-type GaAs substrate 61 having a surface whose normalline is inclined at an angle of 15° in the [011] direction from the(100) plane by the MOCVD method. It is to be noted that the quantum wellactive layer 65 has a well layer of GaInP and a barrier layer of(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P

In this case, the n-type AlAs/n-type Al_(0.5)Ga_(0.5)As 30-pair DBRlayer 63 and the p-type (Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-typeAl_(0.5)In_(0.5)P 12-pair DBR layer 67 are formed so that the reflectionspectrum is centered at a wavelength of 650 nm, and a resonator lengthis adjusted so that the resonance wavelength of the resonator formed ofthe two DBR layers 63 and 67 becomes 650 nm. In the present embodiment,the resonator length was 1.5 times the wavelength. Further, the quantumwell active layer 65 is formed so that the layer is located in the bellyposition of the standing wave generated in the resonator with the lightemission peak wavelength set to 650 nm.

Subsequently, as shown in FIG. 24 and FIG. 25 (sectional view takenalong the arrow line XXV—XXV in FIG. 24), the n-type GaAs cap layer 71is removed by a sulfuric acid/hydrogen peroxide based etchant.Thereafter, the n-type Al_(0.01)Ga_(0.98)In_(0.01)P current constrictionlayer 70 is etched until the etching reaches the p-typeAl_(0.01)Ga_(0.98)In_(0.01)P first current diffusion layer 69 byphotolithography and a sulfuric acid/hydrogen peroxide based etchant. Bythis etching, a circular current path 75 having a diameter of 70 μm isformed.

Next, as shown in FIG. 26 and FIG. 27 (sectional view taken along thearrow line XXVII—XXVII in FIG. 26), a p-typeAl_(0.01)Ga_(0.98)In_(0.01)P second current diffusion layer 72 having afilm thickness of 7 μm is regrown on the n-typeAl_(0.01)Ga_(0.98)In_(0.01)P current constriction layer 70 and thep-type Al_(0.01)Ga_(0.98)In_(0.01)P first current diffusion layer 69. Inthis stage, an Al_(0.01)Ga_(0.98)In_(0.01)P layer that has a latticeconstant about 3.6% smaller than that of the n-type GaAs substrate 61and has a film thickness of about 8 μm is formed on the p-type(Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P/p-type Al_(0.5)In_(0.5)P 12-pair DBRlayer 67, and the wafer surface is a roughened surface.

Subsequently, as shown in FIG. 21 and FIG. 22, AuBe/Au is deposited onthe p-type Al_(0.01)Ga_(0.98)In_(0.01)P second current diffusion layer72, and a surface electrode is formed by photolithography and etchingwith an Au etchant. Then, heat treatment is performed to form a p-typeelectrode 73. Further, the n-type GaAs substrate 61 is abraded to a filmthickness of about 280 μm, and AuGe/Au is deposited on this abradedsurface and subjected to heat treatment to form an n-type electrode 74.

The thus-formed semiconductor light-emitting device does not need theprocess of separately roughening the wafer surface after crystal growthat all, by comparison with the first through third embodiments, allowingthe processes to be simplified. It is to be noted that the radiationangle dependency of the emission light wavelength is slightly greaterthan the dependency of each of the first through third embodiments, asshown in FIG. 28, since the degree of surface roughening is small.However, the dependency is much smaller than in the case where nosurface roughening is performed.

There is, of course, no problem about the moisture resistance. When anelectrification test was performed at a current of 50 mA under theconditions of a temperature of 80° and a humidity of 85%, an opticaloutput of 90% of the initial optical output was yielded even after alapse of 1000 hours. With regard to the initial optical output, asufficiently high optical output of 1.7 mW was obtained at a current of20 mA.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A semiconductor light-emitting device comprising:a resonator including multi-layer reflection films on a GaAs substrateside and a surface side that are formed with interposition of aninterval in a direction perpendicular to the GaAs substrate on the GaAssubstrate, a light-emitting layer formed in an anti-node position of astanding wave between the multi-layer reflection films, and asemiconductor layer which has one or more layers and an uppermostdiffusion layer whose surface comprises roughened means for lightdiffusing which causes light output from the device to be diffused uponleaving said surface of said uppermost diffusion layer, thesemiconductor layer being formed on the multi-layer reflection filmlocated on the opposite side of the GaAs substrate with respect to thelight-emitting layer.
 2. A semiconductor light-emitting device asclaimed in claim 1, wherein the light-emitting layer is constructed ofan Al_(y)Ga_(z)In_(1−y−z)P (0≦y≦1, 0≦z≦1) layer comprised of a singlelayer or a plurality of layers.
 3. A semiconductor light-emitting deviceas claimed in claim 1, wherein the multi-layer reflection film locatedon the GaAs substrate side with respect to the light-emitting layer isan Al_(x)Ga_(1−x)As (0≦x≦1) layer, and the multi-layer reflection filmlocated on the opposite side of the GaAs substrate with respect to thelight-emitting layer is constructed of an Al_(y)Ga_(z)In_(1−y−z)P(0≦y≦1, 0≦z≦1) layer.
 4. The semiconductor light-emitting device ofclaim 1, wherein the diffusion layer comprises a light diffusion layer.5. The semiconductor light-emitting device of claim 1, wherein thediffusion layer comprises a current diffusion layer.
 6. A semiconductorlight-emitting device comprising: a resonator including a pair ofmulti-layer reflection films formed with interposition of an interval ona GaAs inclusive substrate, a light-emitting layer located between themulti-layer reflection films, a semiconductor layer which has one ormore layers and an uppermost diffusion layer whose surface is roughenedin a light diffusing manner so as to cause light output from the deviceto be diffused upon leaving said surface of the uppermost diffusionlayer, the semiconductor layer being formed on the multi-layerreflection film located on the opposite side of the GaAs substrate withrespect to the light-emitting layer, and wherein at least a portion ofthe roughened surface of the semiconductor layer is exposed so that itis not contacted by any metal film.
 7. The semiconductor light-emittingdevice of claim 6, wherein the diffusion layer comprises a lightdiffusion layer.
 8. The semiconductor light-emitting device of claim 6,wherein the diffusion layer comprises a current diffusion layer.
 9. Alight emitting device comprising: a semiconductor substrate; a resonatorincluding first and second multi-layered reflectors supported by thesubstrate; a light emitting layer provided between the first and secondmulti-layered reflectors; a semiconductor diffusion layer supported bythe substrate, with the reflectors being provided between the substrateand the semiconductor layer, the semiconductor diffusion layer includingan uppermost surface which includes a roughened means for causing lightoutput from the device to be diffused upon leaving said roughened meansat said uppermost surface of the semiconductor diffusion layer; adielectric layer provided on the substrate over the semiconductor layer;and an aperture provided in the dielectric layer, the aperture beinglocated over at least part of the roughened means portion of thesemiconductor layer.
 10. The device of claim 9, wherein the dielectriclayer comprises silicon oxide.
 11. The device of claim 9, wherein theroughened means of the semiconductor layer is exposed in the aperture ofthe dielectric layer, and no metal layer is provided over and contactingat least a portion of the roughened means of the semiconductor layer inthe aperture.